Seymour, Missouri has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.9 °C (low) to 18.7 °C (high). Annual precipitation averages 1212.1 Millimeters. Seymour is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5 °C | 5.3 °C | 70.36 mm |
| February | -2.9 °C | 7.9 °C | 72.39 mm |
| March | 1.9 °C | 13.1 °C | 107.7 mm |
| April | 7.3 °C | 18.8 °C | 128.52 mm |
| May | 12.7 °C | 23.7 °C | 146.05 mm |
| June | 17.7 °C | 28.1 °C | 111.76 mm |
| July | 20 °C | 30.7 °C | 109.73 mm |
| August | 19 °C | 30.3 °C | 88.9 mm |
| September | 14.8 °C | 26.4 °C | 106.68 mm |
| October | 8.5 °C | 20.1 °C | 92.46 mm |
| November | 2.8 °C | 13.2 °C | 103.12 mm |
| December | -2.6 °C | 6.9 °C | 74.42 mm |
| Annual | 7.9 °C | 18.7 °C | 1212.09 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |